Thread controlling device for sewing machines



Nov, 20, 1945. F. A SHWORTH 2,389,124

THREAD CONTROLLING DEVICE FOR SEWING MACHINES Filed April 4, 1944 2Sheets-Sheet 1 Eventor FRED ASf/h/OR 77/ Nov 20, 1945, wom- 2,389,124

THREAD CONTROLLING DEVICE FOR SEWING MACHINES Filed April 4, 1944 2Sheets-Sheet 2 Patented Nov. 20, 1945 THREAD GONTROLLING: DEVICE EOE;

Fred Ashworth, Wenham; Mass;, assignor to. United". Shoe MachineryQorporatiomflmihg ton; N. J'-., a corporation of'NewJerseyAipplicatiomAprilA;1944,,SeriaLNmj29a465 10 Gianna.

The: present. invention. relates; to.- improvements.

in thread controlling devices for use. sew n machines: of the: type.intended. for operation: on shoes on other heavy materials and:provided: with a curved hook needle and a take-up acting: to take: up.each. loop of thread; drawn. throu h. the worle by the needle: and togive- 1111 hre d; durin each. sem'ng: cycle at: a. rate greater than;required by the; other stitch. forming. d'evicesrso that the portion:ofi thread: engaging: the. takeeupi becomes slack during a substantialpart of each sewing cycie. An; example: of a machine: of this: type isdisclosed in mated: States Letters Batent: No; 2271 6141; of. February3; 19.42; 015 which: the presinventor: is ioint patentee andi, incertain recspects, the present invention is related to featuresdisclosed in. invlentors. Unitedi States; Lettera FatenlzNo:.Z;35(l,995of June 13;, 19431..

In the machineoi- PatentNo. 2;?37 1,611,.a thread tensioning: deviceacts on. the. thread. b'etweena' the take-up and the last formedistitchthe. work to; keep; those. portions: of the thread engaging: thestitch; forming; devices, other.- than. the take-up; under control.while; the. take-up is giving; up thread to: said other stitch formingdevices. In order.- to. avoid} thev effects of. excessive: friction andabrasion; on; the thread: while: the: taint-upis taking up: thread. andaparticularly while 2i. stitch is; being set, mechanism. driver-r fromthe; main sewingshaft at the patented: machine is provided for.actuating. thetensioning. device: to: relieve the frictional effect on.the; thread in each. sewin cycle.- while. the: ta-keeup. is? taking. up:thread; In the. machine of. Patent. No.. 2,350,995; the; change intension oi; the. thread. is controlled directlsrby the thread. itself.without, theuse of-v any posietively driven actuating, mechanismseparate from the; tensioning; device. The. tensioning device; of Batenh2350 9.95 consists of. a. spring-pressed plate. and astationary' surfacebetween which the threadiia compressed, the arrangement beinasil h thatthe transverse. movement. of. the thread. as a result 0t the action: of.the; take.-up,. causes the thread to move.- along; the plate from. a;position where; the: frictional. tension produced by spring pressure is;greater (hiring. the: giving-up: stroke oi the take-uptoapositionlwherethe pressureis substantially less; during? thatak'e-upu stroke of thetake-up; This: arrangement. is? advantageous in that, it, providesefi'ecti'va control. of the: slack thread during. high: speeds: ofoperation; but. in order to; provide; accurate. control" of the threadunder: all: conditions: of operatiom it: is desirable tm relieve thetension: entirely on the thread dur atportionz of: the" giving-up:stroke: of the takeup; as: Well as; during: the taking-up stroke whileduring the; remainder-01f I the: giving-up stroke; the usuali amount ontension. impartedlhy the spring:- pressed; plate'is needed;

In the operation. of." aihook needle sewing: ma.- chine: after the:needle the work. from. one side andz'emerg'es tromithe other-side, a:vloop. of threadislaid inthe needlehookzbya loopenthe thread having.previousi'y, been enga ed; with. a thread finger-'andmeasuredcfi; fromthe supply sufficiently in. amount tdprovide slack thread; hestween;therpreviously'lormedstitclt andthe needle at least until. theneedle .hnoichas. been withdrawn with the; thread; a. substantial;distance from; the side: of. the: Work. at; which it entered Ifinsufiilcienir. slack: thread; provided between the; last formedi stitchanm the needle to; enable the threaded needle hook. to: pass: through.and: be withdrawn. 2; substantiak distance fr m the Work, thethreadgbetween the; needle; and th r t t may be; pulled ton tightly theneedle hookis being; drawn throughthe: work, at which time, a maximum.amount at abrasion. on; the thread: occurs, the; thread of: the-loop.=carriedby the; needle being compressed in the form. of:a.sharp:=bightintheneedle hook. Under these: conditions a. number:- of. d'rfiiculties;arise; The: abrasion ofithe thread. atthez hight engaging the needlehook may he so: excessive. as; to: strand the. thread, the previnusiyformed: stitch may be. displaced by'stealing' thread; therefrom; or thethread may become stretched excessively or broken,

Mter the threaded needle hasbeen withdrawn fully fromcthe work, themachineisof thelockstitchl type, some form of thread lifter or loopspreader and a. loop taker are employed which enter the loop carriedby'the' needle hook; drawing; thread from: the: supply as the needlecontinuestowithd'raw from the work; S'omesliding movement onreeving ofthe thread through the needle hook iaunavoidable at'this time, but thethread noil'e'nger has a sharpbightf-ormation in the: needle;. so thatthere is lesslikelihood of injury tozthe threadl During this action, thethread is. being: dragged through the needle perforation im the.Worhwhich: itself: causessome tension in the thread. so that control ofthethread onthe needlesideof theaworkis assured. If'at this timefurther: frictional-I drag is imparted by" the tensibnihg: device, thedrag: on the thread while sliding through the needle hook under somecircumstances may be excessive If no drag atall is imparted to the:thread beneath the work at the take-un side; there: may be:- other'undesirable resultsttolbezexplained;

During the transfer of the needle loop from the thread lifter and needleto the loop taker, the speed of movement of the thread, as it is beingwithdrawn from the work, changes abruptly, being withdrawn at firstrapidly by the thread lifter and then more slowly as the loop is enteredby the loop taker. If the thread between th take-up and the work issubstantially free of tension at this time, the momentum of the threadunder movement of the thread lifter will carry the thread beneath thework out of its straightline path between the take-up and the work,

causing it to twist and slap against adjacent parts tends to applyperiods of momentary erratic resistance to the movement of thethread,'contributing to non-uniformity in movements of the thread whilebeing disengaged from the thread lifter and engaged by the loop taker.-Non-uniformity in movements of the thread during for-. mation of astitch at this time is reflected in irregularly formed stitches andvarying tensions in the threads of completed stitches.

One object of the present invention is to provide a curved h'ook needlesewing machine of the type referred to which will insert an extremelyuniform seam with little or no abrasion to the thread and in which thedifficulties above enumerated are overcome. Another object is tosimplify and improve the construction and mode of operation of alockstitch shoe sewing machine, particularly with respect to regularityof stitch formation and location of stitches in the work operated upon.Another object of the invention is to provide a frictional threadtensioning device between the take-up and the work for a lockstitchsh'oe sewing machine which will operate in a desirable manner and willprevent erratic movements in the thread during the iving-up strokeof thetake-up as a result of changes in velocity. of thread movement,particularly while each needle loop isbeing transferred from the needleto the loop taker.

In the illustrated embodiment of the invention, a hook needle sewingmachine, having a needle loo-per for laying, the .thread in the needlehook and a take-up, is equipped with means acting on the needle threadbetween the take-up and the looper to cause tension to be imparted tothe thread while the thread is being laid in the needle hook and,thereafter, to relieve the tension on the thread, at least until thehook of the needle has drawn the bight in the thread loop' carriedthereby into the work. Preferably, the tension imparting means consistsof a device actuated during each sewing cycle by suitable positivelydriven mechanism rather than depending wholly upon the movements of thethread while being acted upon by the take-up, and in the illustratedform of this feature the tensioning device is actuated to relieve thetension until the needle has withdrawn its loop from the work. At thetime of withdrawal, while the needle still engages the thread, the loopis first entered by the thread lifter, the lifter in the form of theinvention hereinafter described havingsubstantially reached the extremeend of its. spreading movement before the tension is reapplied. In orderto prevent irregular movements of the thread while the needle loop isbeing transferred from the thread lifter to the loop taker, the tensionis again applied to the thread by the tensioning device just before theloop escapes from'the needle and lifter, thus preventing the threadbetween the take-up and the looper from becoming loose as a result ofits inertia and slapping against the adjacent machine parts or portionsof the work.

These and other features of the invention consist of the novelconstructions, combinations and arrangements of parts, as will becomemore fully apparent from the following detailed specification taken inconnectionwith the accompanying drawings, in which Fig. l is a view inleft-hand side elevation of so much of a curved hook needle lockstitchshoe sewing machine as is necessary for an illustration of an embodimentof the present invention, the parts of the machine being indicated inpositions assumed while the needle is being looped;

Fig. 2 is a similer view of the same portions of the machine illustratedin Fig. l with the parts in positions assumed after the needle has beenwithdrawn from the work with its loop of thread and the loop isbeingretracted toward stitch setting position;

Fig- 3 is a detail view on an enlarged scale of a tension releasingmember illustrated in Figs. 1 and 2;

Fig. 4 is another detail view on a similar scale of the tensionreleasing member illustrated in Fig. 3, together with a connecting rodfor actuating the tensioning device, the parts being viewed at rightangles to the direction in which Fig. 3 is taken;

Fi 5 is a sectional view on an enlarged scale taken along the line VV ofFig. 1;

Fig. 6 is a detail view of a yielding tensioning plate forming themovable part of the tensioning device;

Fig. 7 is a detail view on a slightly enlarged scale of some of theparts of the machine illustrated in Fig. l in positions assumed at thetime in each sewing cycle when the frictional tension 'on the thread isrelieved;

Fig. 8 is a similar view of the parts in positions assumed while aneedle loop is being transferred from the loop spreader to the looptaker; v

Fig. 9 is a view on a still further enlarged scale of a portion of thehousing for the take-up, indicating the cover for the housing in closedposition and the tensioning device operative, and

Fig. 10 is a plan view of the take-up housing and tensioning deviceillustrated in Fig. 9.

The machine illustrated in the drawings is a lockstitch shoe outsolesewing machine having a curved hook needle 2, a continuously rotatingtake-up 4, a looper 6, a thread finger 8, a loop taker or shuttle l0enclosing a thread case ll having a supply of locking thread, a threadlifter or loop spreader [2 for opening each needle loop for the shuttle,and other stitch forming devices similar in construction and mode ofoperation except as hereinafter pointed out to those disclosed in PatentNos. 2,271,611 and 2,350,995 above referred to. As in the machine ofthepatents, the stitch forming devices are so operated thatsubstantially no tension will be imparted to the needle thread l3 by thetake-up in each sewing cycle except when each stitch is being set. Tocontrol the needle'thread while each loop is being formed and carriedabout the thread case in the machine of the patents, a frictional threadtensioning device is provided between the take-up and the work so thatsufficient'tension will be applied to the thread between the time theneedle is looped and drawn throughthe work and the time the needleloopreaches a position of maximum extension about the thread case, thetensioning device assisting theneedlelooping' oper ation and preventingdisplacement at the thread fromthe hookof the needl'e asthe threadedneedle movesupwardly'through the work; The ten sioning' device ofPatent- No. 2350,9953 is mounted directly upon astationarycircularlyflanged shield comprising a housing for the take-up, acorresponding flanged shield being indicated at I 4 in thepresentillustrated machine Cooperating with the shield: I4 to prevent escape ofthe needle thread: from control. of the take-up is a cover: plate L6?hingedly mounted onipins l3=- on the take-uphousing;

The take-up 4 consistsof. an arm rotating con tinuou'sly in the.direction ot the arrow between the cover and thezshield with.atake-upshaitZO passing throughsthe shield. and? carrying. thetakeup arm at oneend. The rotation of-v the-shaft 20 is: timed with. the. operation of.the. other stitch forming; devices to. causethe threadiengaging. thetake-up.- to. be: given. upv as; the looper 6 lays the thread in the.hook of the. needle. The. needle draws the thread into a loop while.moving up.- wardly. through the work, thetwosides of the loop forming.a, sharp. bight engaging. the. needle. While the thread bight of.theneedle loop isibeing carried through the. workwith the needle hook,itis subject. to substantial compression. against the. inner surfacesof. the needle perforation and to frictional abrasion. The compression:of: the thread in the bight carried by the needle varies with; the typeof work operated upon and,.in.some

instances,v may produce excessive. friction. and

abrasion and injury to the thread.v

To avoid unnecessary injury to the: thread in many sewing machines ofthe hook needle. type, a predetermined length is: measured. between thethread finger and the last. formed stitch. in the work, as illustratedin Fig, 1, before the looper lays the thread in the needle hook. Thelength of thread thus measured is intended to enable passage of theneedle loop through the work without requiring sliding movement. of thethread through the needle hook. In many machines heretofore usedcommercially, the threadis kept under controlby actuating, the take-upto give up thread. only in the. amount required, noslack. be.-ingpermitted. The take-up 4: of. the machine disclosed in the patents isactuated to" provide slack threadby giving upmore thread than isrequired for the needle looping. operation. and the tensioningdevice onthe take-up housing im-' parts only a lightfrictional. drag on. thethread tokeep the thread between the tensioning device and. the work.under just enough tension to insure laying. the thread securelywithinthe needle hook. ssoon as the thread is laid in the needle hook,however, the thread finger moves to give up its supply of measuredthread and, inv so do ing, reduces the tension in that part of thethread between the needle hook and the. last formed stitch. Tension inthe thread between the needle hookand the tensioning device. atthis timemay cause the thread to slidein the needle hook before the. threadedhook enters. the work since the thread tends. to move. in the directionof greatest tension. The. result ofsuch sliding movement is to cause atleast partial loss of thread: measured. by the. thread finger so thatthe thread. between the needle and. the last formed stitch may be.subject to the same excessive tension and abrasion beforethe threadedneedle hook is withdrawnv from the opposite side. of. the work, asthough no measurement-had. occurred. Ifthe thread is exceptionallystrong, satisfactory stitches: may still be formed even. under theseconditions, particularly where: excessively large size of needle hook:is; employed. orthe: ma.- chine is operated at. slowspeeds: Witha.small.- sized needle: hook as: compared to. the size; of threadutilized, itis; necessary to compress; the thread tightly intdthe.hoolnirr order to prevent a few strands from escaping and, withrelatively poor: walityfthread any tendency: to; slide in theneedleshook; before; the threaded needle is. with.- drawn from theworlqsubiectszthethreadzto C61?- taimihjury. or breakagez.

Toiovercomathesedifficulties, while ati-thezsame enabling easy'passage:of the needlev thread through the work without. liability of: injury orexcessive abrasion". on. the: thread inth'e. machine embodying the;teat-ureszoi the present invention, the take-up housing: has; mountedon. it av triotionalrtensioniherdeviceactuatedlahsuitableztimes bathrbytransverse movement of the: thread and by separate mechanism to. change;the. tension in the. threadin a desiredimanner; The tensioning device.comprises; a. vertical plate 22: backed atits forward; endby; a. pair.of spring-pressed. plungers Pal: slidingly. mountedinhorizontalpassagesin the take-uphousing. At.it's rearward end, the platehas;:a horizontal: slotted tab slidingly mounted in a: cut: formed in.a. block: 26 securedv to. they housingl. Td-hoId the tab loosely inposition, theblock has a vertical passage into which isdriven arepiILZB; entering the: slot. in the tab. At its forward end,. the:tensioning plate has. an open slot. to: receive a horizontal:positioning pin 29 secured; in: the; takeZ-up. housing.

mtheitensioningrdevice oi-Patent No. 2,350,995,theztensioningplateis.drawnagainst a horizontal surface of a. blUCkE on.the. housing for the takeupr;.requiringithe'threadito be introducedbetween the plate anldablocls while threading'themachine. In: thepresent-J illustrated machine, the necessity ofintroducing the-threadbetween the tensioning plate and the; supporting. block is avoided, thetensinning. plate being: pressedv by the plungers 24againstahorizontalihiction surface on a block 38 secured. by means orscrews: 32 to the take-up cover: plate; 162. The: arrangement is: suchthat, with; the thread. located. in. operating position" on the take-upwhile the cover plate. It is open during: threading: of the. machine,proper location or the thread. witlt respect to the tensioning plateiginsnred' when; the. take-up cover plate is'closed.

The: operatiomof thetensioning plate 22 in imparting", tension to.thethread is. substantially the same as that; in. Patent No.. 2,350,995in which there lSi a. very light frictional pressure on the threadwhilezt'he. takei-uplis takingup-thread from the otherstitchformingrdevices', as in Fig. 2, thus avoiding unnecessary abrasion onthe thread.

While the take-up isstaking: up: thread, the-thread is; drawn. against:a. flanged. guide wheel 34' rotatable on a screw 36 threaded. into theblock 26. When the take-up reaches the lower end of its takingrup strokeafter. the stitch being formed is set. in the work, the. thread betweenthe take-up andat'he l'ooper: movesv transversely oi its length away'from the guide wheel 34: and, thereafter, the: stitch setting: tension.on the thread is sub- 1 stantially' relieved; Asisoonas the take-upbegins its; giving-up strokathe. thread is engaged with the threadfinger 8 (Fig. 1i) and is laid in the hook of. the-needle by'tha l'ooper6, the take-up providing;- slacl'c thread. during these operations. In:moving: away, from the guide wheel 34, the thread is carried forwardlytoward the portion of I the tensioning; plate acted upon by the plungers24. While engaged by that portion of the tension plate acted upon by theplungers 24, a substantial amount of frictional tension is imparted tothe thread. In addition to operation of the tensioning device bytransverse movement of the thread, it is also actuated by suitablemechanism to prevent loss in thread measured by the thread finger.

The mechanism for actuating the tensioning device apart from thetransverse movements of the thread includes a swinging tension releasemember 31 pivotally mounted at 38 in a lug 40 located within a radialdepression 42 formed in 'the Shield [4. The lug 40 is located near thetakeup shaft on the shield, and the release member is bifurcated toembrace the lug at one end. At its other end, the release member isprovided with an arcuate extension having a cam surface 44 disposedwithin the rotary path of the takeup to be actuated thereby. Between therelease member and the shield, there is a compression spring 46 forpressing the release member into the path of the take-up. The camsurface 44 is so shaped that, during the giving-up stroke of thetake-up, the release member will be swung about its pivot 38 at a timein the sewing cycle directly after the thread is laid in the hook of theneedle 2 and before substantial forward thread releasing movement of thethread finger occurs '(see Fig. 7)

The connections between the release member .31 and the tension platecomprise an upwardly extending arm on the release member having itsupper extremity fitting within a slot in a horizontal connecting rod 48slidingly mounted in a suitable guideway in the take-up housing beyondthe range of the take-up path. Diametrically opposite to the releasemember receiving slot in the connecting rod 48 and at its other end, isa second slot into which is loosely engaged an extension of thetensioning plate 22, the parts being so arranged that, when the releasemember is engaged by the take-up, the tensioning plate is moved awayfrom the thread engaging surface of the block 30, thereby relieving thecompression on the thread. The tension on the thread between thetensioning device and the work is held relieved in this way until afterthe threaded needle has fully been withdrawn from the work and thethread lifter I2 has not only entered and spread the needle loop but hasapproached the extreme end of its loop spreading movement. At this time,the shuttle is beginning to enter the loop spread by the thread lifter,as best, shown in Fig. 8. As the thread lifter approaches the extremeupper end of its loop spreading movement, its rate of travel is retardedso that, unless tension is immediately applied to the thread between thetakeup and the work, there will be an opportunity for the thread to whipand become displaced, twisting itself around adjacent parts,particularly the looper, or slapping against the upper of a shoe beingoperated upon, in an irregular manner indicated by the dot-dash lines.When the machine is operating at high speeds, such irregular movementsof the thread impart momentary tension and resist uniform movements ofthe thread in the needle loop from one sewing cycle to another, tendingto cause breakage or imperfect stitch formation. As soon as the shuttleenters a needle loop, the thread is disengaged, first from the needleand then from the thread lifter, and is carried about the thread case inthe usual way.

At all other times in each sewing cycle, the

tension device is effective to maintain the thread between the take-upand the work under control in the same manner as that disclosed ininventors Patent No. 2,350,995, the temporary relief of tension on thethread occurring only between the times the needle is looped and theapproach of the thread lifter to the extreme end of its loop spreadingmovement before the loop has been disengaged from the needle and threadlifter. Relief of the tension on the needle thread in this way not onlyis advantageous in preventing non-uniform sliding movements in the hookof the needle and elsewhere and consequent abrasion of the thread whileeach needle loop is being drawn through the work but also assists in auniform location of the spread loop for the shuttle and a subsequentuniform loop spreading action of the shuttle in opening up the loop forits passage about the thread case during each sewing cycle. Uniformmovements of the loop during the formation or" each stitch are conduciveto uniform location and setting of stitches in the work. A secondaryadvantage, resulting from the actuation of the tensioning devicedirectly from the take-up, rather than from mechanism actuated by themain sewing shaft as in the machine of Patent No. 2,271,611, followsfrom the use of a relatively simple mechanism for relieving the tensionpositively in addition to its variation as the result of transversethread movement.

The nature and scope of the invention having been indicated and aparticular embodiment thereof having been specifically described, whatis claimed is:

1. A sewing machine having a hook needle, a looper for laying the threadin the needle hook and a take-up, in combination with means acting onthe needle thread between the take-up and thelooper tocause tension tobe imparted to the thread while the thread is being laid in the needlehook and to relieve the tension on the thread after the thread is laidin the needle hook until the hook of the needle has drawn the threadinto the work.

2. A sewing machine having a hook needle, a looper for laying a loop ofthread in the needle hook, a thread finger for measuring thread betweenthe needle and the last-formed stitch in the work and for giving up themeasured thread after the thread is laid in the needle hook, a takeup,mechanism for actuating the take-up to provide slack in the needlethread as the needle hook carries each needle loop through the work andto set each stitch, and a tensioning device acting on the thread betweenthe take-up and the looper, in combination with mechanism for actuatingthe tensioning device during each sewing cycle to relieve the tension onthe thread after being laid in the needle hook and until the hook of theneedle has drawn the needle loop into the work.

3. A sewing machine having a hook needle, a looper for laying a loop ofthread in the needle hook, a thread finger for measuring thread betweenthe needle and the last-formed stitch in the work and for giving up themeasured thread after the thread is laid in the needle hook, a takeup,mechanism for actuating the take-up to provide slack in the needlethread as the needle hook carries each needle loop through the work andto set each stitch, and a tensioning device acting on the thread betweenthe take-up and the looper, in combination with mechanism for actuatingthe tensioning device during each sewing cycle to relieve the tension onthe thread before the hook of the needle draws the needle loop into thework and until the needle has withdrawn the loop from the work.

4. A lockstitch sewing machine having stitch forming devices including ahook needle, a looper, a locking thread case, a rotary loop taker forpassing loops of needle thread over the'thread case, a thread lifter forspreading each needle loop for the loop taker, a continuously rotatingtake-up arranged to provide slack in the needle thread as each needleloop is being drawn through the work by stitch forming devices otherthan the take-up and to pull each needle loop from the loop taker, and africtional tensioning device acting with a yielding pressure on thethread between the looper and the take-up, in combination with mechanismfor actuating the tensioning device during each sewing cycle to relievethe tension on the thread before the hook of the needle draws the threadinto the work and until the thread lifter approaches the extreme end ofits loop spreading movement.

5. A lockstitch sewing machine having stitch forming devices including ahook needle, a looper, a locking thread case, a rotary loop taker forpassing loops of needle thread over the thread case, a continuouslyrotating take-up arranged to provide slack in the needle thread as eachneedle loop is being drawn through the work by stitch forming devicesother than the take-up and to pull each needle loop from the loop taker,and a frictional tensioning device acting with a yielding pressure onthe thread between the looper and the take-up and comprising membershaving opposed thread engaging surfaces, in combination with a tensionrelease member actuated by the take-up, and a connection between thetension release member and one of the tensioning members acting toseparate the members while the needle is being looped and before thehook of the threaded needle enters the work.

6. A lockstitch sewing machine having stitch forming devices including ahook needle, a looper, a locking thread case, a rotary loop taker forpassing loops of needle thread over the thread case, a continuouslyrotating take-up arranged to provide slack in the needle thread as eachneedle loop is being drawn through the work by stitch forming devicesother than the take-up and to pull each needle loop from the loop taker,and a frictional tensioning device located outside the rotary path ofthe take-up to act on the thread between the looper and the take-up, incombination with a tension release member located within the rotary pathof the take-up to be actuated thereby, and a connecting rod between thetension release member and the tensioning device.

'7. A sewing machine having stitch forming devices including a hookneedle, a take-up acting to take up and give up thread and to move thethread transversely of its length, and a frictional tensioning deviceconstructed and arranged to impart a variable tension to the thread thevariation of which is controlled by transverse movement of the threadbetween the take-up and the work, in combination with mechanism foractuating the tensioning device to relieve the tension on the threadduring each sewing cycle beIore the hook of the needle has drawn thethread into the work.

8. A sewing machine having stitch forming devices including a hookneedle and a take-up, a shield for the take-up, and a hinged cover toenclose the take-up in the shield, in combination with a frictionaltensioning device acting on the thread and comprising members havingthread engaging surfaces, one of which is carried by the cover and oneof which is actuated by the takeup toward and from the other member.

9. A sewing machine having stitch forming devices including a hookneedle, a looper for laying a loop of thread in the needle hook, acontinuously rotating take-up arranged to provide slack in the needlethread as each needle loop is being drawn through the work by stitchforming devices other than the take-up and to pull each needle loop intothe work, a shield for the take-up, and a hinged cover plate to enclosethe take-up in the shield, in combination with a frictional tensioningdevice acting on the thread and comprising members having threadengaging surfaces, one of which is carried by the cover plate and theother of which is mounted on the shield for relative movement toward andfrom the tensioning member on the cover plate while the cover plate isclosed, and mechanism actuated by the take-up to separate the tensioningmembers between the times in each sewing cycle when the thread is laidin'the hook of the needle by the looper and when the needle draws thethread into the work.

10. A sewing machine having stitch forming devices including a, hookneedle, a looper for laying a loop of thread in the needle hook, acontinuously rotatin take-up arranged to provide slack in the needlethread as each needle loop is being drawn through the work by stitchforming devices other than the take-up and to pull each needle loop intothe work, a shield for the take-up, and a hinged cover plate to enclosethe take-up in the shield, in combination with a frictional tensioningdevice acting on the thread and comprising members having threadengaging surfaces, oneof which is carried by the cover plate and theother of which is mounted on the shield for relative movement toward andfrom the tensioning member on the cover plate while the cover plate isclosed, a tension release member mounted on the shield within the rotarypath of the take-up to be actuated thereby, and a connecting rod betweenthe tension release member and the tensioning plate slidingly mounted onthe shield for separating the tensioning members when the take-upengages the tension release member.

FRED ASHWOR'I'I-I.

